The present invention relates generally to devices that are mounted on vehicles to operate safety units associated with the vehicle, such as crossing arms, stop signs and the like which are mounted on school buses for selective movement outwardly therefrom to form barriers or warning devices.
It is, of course, well known that children, particularly young children, who are transported in school buses are vulnerable to accidents involving the school bus or the children themselves during the time they are leaving or approaching the school bus, and it is therefore common practice to provide school buses with safety units that are designed to reduce the risk of such accidents.
One familiar safety unit that is almost universally found on school buses is the octagonal stop sign that is usually mounted on one side of the school bus, and that is movable from a normal retracted position along the side of the school bus to an extended position projecting outwardly from the side of the bus to warn other motorists that children are leaving or approaching the school bus so that such motorists can stop all movement of their vehicles until the children have safely boarded the bus or cleared the area after leaving the bus. Typical stop sign safety devices of this type are disclosed in Latta U.S. Pat. Nos. 4,138,668; 4,339,744; and 4,559,518.
Another familiar safety unit frequently found on school buses is a crossing arm that is usually mounted on the front bumper of the school bus and that is arranged for pivotal movement from a first retracted or passive position, at which the generally lengthy crossing arm extends along and adjacent the bumper, to a second active position at which it extends outwardly and generally perpendicular with respect to the bumper, thereby providing a barrier that encourages children to walk in a path well away from the front bumper of the school bus so that the driver of the school bus can readily see the children and avoid moving the bus until they have cleared the area in front of the bus. The construction and operation of crossing arms of this type are disclosed in greater detail in Latta U.S. Pat. No. 4,559,518, Wicker U.S. Pat. No. 4,697,541 and Runkle U.S. Pat. No. 3,153,398.
As discussed in the above-identified prior art patents, the actuating devices for moving the safety units between their retracted and deployed or extended positions may be vacuum (or air) operated, or they may be electrically operated, and such actuating devices are generally designed to stop movement only at the retracted and deployed positions. However, since the safety units, at their deployed positions, are extending outwardly and generally perpendicularly from the school bus, they invite the attention of children, and others, and offer a tempting target to be pushed away from such extended position by the children passing by the extended safety unit. Also, even in their retracted positions, the safety units present a temptation for children to pull them outwardly from such retracted position. Obviously, if the actuating device for the safety unit included only a rigid drive connection between the operating mechanism (e.g. electric motor) and the movable safety unit, any such manual pushing or pulling force applied directly to the safety unit could damage or even destroy the operating mechanism of the actuating device.
To overcome this problem, it is now common practice to provide safety unit actuating devices with a double-acting hinge construction of the type generally disclosed in Latta U.S. Pat. No. 4,138,668 that includes relatively heavy coil springs that are arranged to resist any manual movement of the safety unit from its set position, and, if a manual force is applied to the safety unit of sufficient magnitude to move the safety unit from its set position, the springs will return the safety unit to its original set position. Also, there is another known hinge device that accomplishes generally the same function as the aforesaid double-acting hinge by utilizing a combination of a biasing spring and cam surface arrangement, whereby manual movement of the safety unit causes the cam to move along a cam surface until the safety unit is released, and the spring then returns the safety unit to its extended position. The cam surface has a configuration such that if the safety units moved within a predetermined range from its extended position, it will return to its extended position, but if it is moved beyond such predetermined range and toward its retracted position, it will be moved by the spring to the retracted position rather than returned to the extended position. An example of this type of hinge device is disclosed in U.S. Pat. No. 4,766,413.
More recently in my copending U.S. patent application Ser. No. 303,849, filed Jan. 30, 1989, an improved actuating device is disclosed which includes, in lieu of the aforesaid hinges, a slip clutch between the drive motor and the safety unit support that causes the safety unit to normally be positively moved from its retracted position to its deployed position, or vice versa, and which also permits relative movement of the safety unit with respect to the drive motor when a predetermined force is applied to the safety unit, such as the manual pushing and pulling thereof by a child. Several control circuits are also provided for returning the safety unit to its retracted or deployed position from which it has been moved.
In all of the aforesaid devices, the safety unit (e.g. crossing arm) is driven by an actuator, which may be an electric, air, or vacuum motor, that first moves the safety unit from a stationary retracted position adjacent the bus to a stationary deployed position, at which it remains for a period of time until its intended purpose has been accomplished (e.g. all the children have passed safely across the extended crossing area at the front of the bus). Then, the drive motor is reactivated to return the safety unit to its retracted position where it remains until it is needed again. With regard to crossing arms located on the front bumper of the bus, it is generally desirable to actuate the drive motor when the door of the school bus is first opened, whereby the crossing arm will be moved to its stationary extended position prior to the children leaving the bus, or at least prior to the time when they have left the bus and reached the front of the bus.
While such extended stationary crossing arms provide an effective barrier that normally forces children to follow a path of movement that keeps them within the sight of the operator of the school bus, it is still possible that a child leaving the bus may decide to walk along and immediately adjacent the front bumper of the school bus and then stop when he or she reaches the point at which the innermost end of the crossing arm is joined to the bumper of the school bus, which would defeat the purpose of the crossing arm since the child would be located directly in front of the bus and possibly out of the line of vision of the school bus operator seated in the bus. Obviously, under these circumstances a serious accident could occur if the operator retracts the crossing arm and drives the bus forward.
The present invention provides a safety unit actuating device which is designed to substantially eliminate the likelihood of such a serious accident occurring and to provide additional desirable safety features not found in known devices of this type.